guix.texi

@deftp {Data Type} modem-manager-configuration
Data type representing the configuration of ModemManager.

@table @asis
@item @code{modem-manager} (default: @code{modem-manager})
The ModemManager package to use.

@end table
@end deftp

@cindex NetworkManager

@defvr {Scheme Variable} network-manager-service-type
This is the service type for the
@uref{https://wiki.gnome.org/Projects/NetworkManager, NetworkManager}
service. The value for this service type is a
@code{network-manager-configuration} record.

This service is part of @code{%desktop-services} (@pxref{Desktop
Services}).
@end defvr

@deftp {Data Type} network-manager-configuration
Data type representing the configuration of NetworkManager.

@table @asis
@item @code{network-manager} (default: @code{network-manager})
The NetworkManager package to use.

@item @code{dns} (default: @code{"default"})
Processing mode for DNS, which affects how NetworkManager uses the
@code{resolv.conf} configuration file.

@table @samp
@item default
NetworkManager will update @code{resolv.conf} to reflect the nameservers
provided by currently active connections.

@item dnsmasq
NetworkManager will run @code{dnsmasq} as a local caching nameserver,
using a "split DNS" configuration if you are connected to a VPN, and
then update @code{resolv.conf} to point to the local nameserver.

@item none
NetworkManager will not modify @code{resolv.conf}.
@end table

@item @code{vpn-plugins} (default: @code{'()})
This is the list of available plugins for virtual private networks
(VPNs).  An example of this is the @code{network-manager-openvpn}
package, which allows NetworkManager to manage VPNs @i{via} OpenVPN.

@end table
@end deftp

@cindex Connman
@deffn {Scheme Variable} connman-service-type
This is the service type to run @url{https://01.org/connman,Connman},
a network connection manager.

Its value must be an
@code{connman-configuration} record as in this example:

@example
(service connman-service-type
         (connman-configuration
           (disable-vpn? #t)))
@end example

See below for details about @code{connman-configuration}.
@end deffn

@deftp {Data Type} connman-configuration
Data Type representing the configuration of connman.

@table @asis
@item @code{connman} (default: @var{connman})
The connman package to use.

@item @code{disable-vpn?} (default: @code{#f})
When true, disable connman's vpn plugin.
@end table
@end deftp

@cindex WPA Supplicant
@defvr {Scheme Variable} wpa-supplicant-service-type
This is the service type to run @url{https://w1.fi/wpa_supplicant/,WPA
supplicant}, an authentication daemon required to authenticate against
encrypted WiFi or ethernet networks.
@end defvr

@deftp {Data Type} wpa-supplicant-configuration
Data type representing the configuration of WPA Supplicant.

It takes the following parameters:

@table @asis
@item @code{wpa-supplicant} (default: @code{wpa-supplicant})
The WPA Supplicant package to use.

@item @code{dbus?} (default: @code{#t})
Whether to listen for requests on D-Bus.

@item @code{pid-file} (default: @code{"/var/run/wpa_supplicant.pid"})
Where to store the PID file.

@item @code{interface} (default: @code{#f})
If this is set, it must specify the name of a network interface that
WPA supplicant will control.

@item @code{config-file} (default: @code{#f})
Optional configuration file to use.

@item @code{extra-options} (default: @code{'()})
List of additional command-line arguments to pass to the daemon.
@end table
@end deftp

@cindex iptables
@defvr {Scheme Variable} iptables-service-type
This is the service type to set up an iptables configuration.  iptables is a
packet filtering framework supported by the Linux kernel.  This service
supports configuring iptables for both IPv4 and IPv6.  A simple example
configuration rejecting all incoming connections except those to the ssh port
22 is shown below.

@lisp
(service iptables-service-type
         (iptables-configuration
          (ipv4-rules (plain-file "iptables.rules" "*filter
:INPUT ACCEPT
:FORWARD ACCEPT
:OUTPUT ACCEPT
-A INPUT -p tcp --dport 22 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-port-unreachable
COMMIT
"))
          (ipv6-rules (plain-file "ip6tables.rules" "*filter
:INPUT ACCEPT
:FORWARD ACCEPT
:OUTPUT ACCEPT
-A INPUT -p tcp --dport 22 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp6-port-unreachable
COMMIT
"))))
@end lisp
@end defvr

@deftp {Data Type} iptables-configuration
The data type representing the configuration of iptables.

@table @asis
@item @code{iptables} (default: @code{iptables})
The iptables package that provides @code{iptables-restore} and
@code{ip6tables-restore}.
@item @code{ipv4-rules} (default: @code{%iptables-accept-all-rules})
The iptables rules to use.  It will be passed to @code{iptables-restore}.
This may be any ``file-like'' object (@pxref{G-Expressions, file-like
objects}).
@item @code{ipv6-rules} (default: @code{%iptables-accept-all-rules})
The ip6tables rules to use.  It will be passed to @code{ip6tables-restore}.
This may be any ``file-like'' object (@pxref{G-Expressions, file-like
objects}).
@end table
@end deftp

@cindex NTP (Network Time Protocol), service
@cindex real time clock
@defvr {Scheme Variable} ntp-service-type
This is the type of the service running the @uref{http://www.ntp.org,
Network Time Protocol (NTP)} daemon, @command{ntpd}.  The daemon will keep the
system clock synchronized with that of the specified NTP servers.

The value of this service is an @code{ntpd-configuration} object, as described
below.
@end defvr

@deftp {Data Type} ntp-configuration
This is the data type for the NTP service configuration.

@table @asis
@item @code{servers} (default: @code{%ntp-servers})
This is the list of servers (host names) with which @command{ntpd} will be
synchronized.

@item @code{allow-large-adjustment?} (default: @code{#f})
This determines whether @command{ntpd} is allowed to make an initial
adjustment of more than 1,000 seconds.

@item @code{ntp} (default: @code{ntp})
The NTP package to use.
@end table
@end deftp

@defvr {Scheme Variable} %ntp-servers
List of host names used as the default NTP servers.  These are servers of the
@uref{https://www.ntppool.org/en/, NTP Pool Project}.
@end defvr

@cindex OpenNTPD
@deffn {Scheme Procedure} openntpd-service-type
Run the @command{ntpd}, the Network Time Protocol (NTP) daemon, as implemented
by @uref{http://www.openntpd.org, OpenNTPD}.  The daemon will keep the system
clock synchronized with that of the given servers.

@example
(service
 openntpd-service-type
 (openntpd-configuration
  (listen-on '("127.0.0.1" "::1"))
  (sensor '("udcf0 correction 70000"))
  (constraint-from '("www.gnu.org"))
  (constraints-from '("https://www.google.com/"))
  (allow-large-adjustment? #t)))

@end example
@end deffn

@deftp {Data Type} openntpd-configuration
@table @asis
@item @code{openntpd} (default: @code{(file-append openntpd "/sbin/ntpd")})
The openntpd executable to use.
@item @code{listen-on} (default: @code{'("127.0.0.1" "::1")})
A list of local IP addresses or hostnames the ntpd daemon should listen on.
@item @code{query-from} (default: @code{'()})
A list of local IP address the ntpd daemon should use for outgoing queries.
@item @code{sensor} (default: @code{'()})
Specify a list of timedelta sensor devices ntpd should use.  @code{ntpd}
will listen to each sensor that acutally exists and ignore non-existant ones.
See @uref{https://man.openbsd.org/ntpd.conf, upstream documentation} for more
information.
@item @code{server} (default: @var{%ntp-servers})
Specify a list of IP addresses or hostnames of NTP servers to synchronize to.
@item @code{servers} (default: @code{'()})
Specify a list of IP addresses or hostnames of NTP pools to synchronize to.
@item @code{constraint-from} (default: @code{'()})
@code{ntpd} can be configured to query the ‘Date’ from trusted HTTPS servers via TLS.
This time information is not used for precision but acts as an authenticated
constraint, thereby reducing the impact of unauthenticated NTP
man-in-the-middle attacks.
Specify a list of URLs, IP addresses or hostnames of HTTPS servers to provide
a constraint.
@item @code{constraints-from} (default: @code{'()})
As with constraint from, specify a list of URLs, IP addresses or hostnames of
HTTPS servers to provide a constraint.  Should the hostname resolve to multiple
IP addresses, @code{ntpd} will calculate a median constraint from all of them.
@item @code{allow-large-adjustment?} (default: @code{#f})
Determines if @code{ntpd} is allowed to make an initial adjustment of more
than 180 seconds.
@end table
@end deftp

@cindex inetd
@deffn {Scheme variable} inetd-service-type
This service runs the @command{inetd} (@pxref{inetd invocation,,,
inetutils, GNU Inetutils}) daemon.  @command{inetd} listens for
connections on internet sockets, and lazily starts the specified server
program when a connection is made on one of these sockets.

The value of this service is an @code{inetd-configuration} object.  The
following example configures the @command{inetd} daemon to provide the
built-in @command{echo} service, as well as an smtp service which
forwards smtp traffic over ssh to a server @code{smtp-server} behind a
gateway @code{hostname}:

@example
(service
 inetd-service-type
 (inetd-configuration
  (entries (list
            (inetd-entry
             (name "echo")
             (socket-type 'stream)
             (protocol "tcp")
             (wait? #f)
             (user "root"))
            (inetd-entry
             (node "127.0.0.1")
             (name "smtp")
             (socket-type 'stream)
             (protocol "tcp")
             (wait? #f)
             (user "root")
             (program (file-append openssh "/bin/ssh"))
             (arguments
              '("ssh" "-qT" "-i" "/path/to/ssh_key"
                "-W" "smtp-server:25" "user@@hostname")))))
@end example

See below for more details about @code{inetd-configuration}.
@end deffn

@deftp {Data Type} inetd-configuration
Data type representing the configuration of @command{inetd}.

@table @asis
@item @code{program} (default: @code{(file-append inetutils "/libexec/inetd")})
The @command{inetd} executable to use.

@item @code{entries} (default: @code{'()})
A list of @command{inetd} service entries.  Each entry should be created
by the @code{inetd-entry} constructor.
@end table
@end deftp

@deftp {Data Type} inetd-entry
Data type representing an entry in the @command{inetd} configuration.
Each entry corresponds to a socket where @command{inetd} will listen for
requests.

@table @asis
@item @code{node} (default: @code{#f})
Optional string, a comma-separated list of local addresses
@command{inetd} should use when listening for this service.
@xref{Configuration file,,, inetutils, GNU Inetutils} for a complete
description of all options.
@item @code{name}
A string, the name must correspond to an entry in @code{/etc/services}.
@item @code{socket-type}
One of @code{'stream}, @code{'dgram}, @code{'raw}, @code{'rdm} or
@code{'seqpacket}.
@item @code{protocol}
A string, must correspond to an entry in @code{/etc/protocols}.
@item @code{wait?} (default: @code{#t})
Whether @command{inetd} should wait for the server to exit before
listening to new service requests.
@item @code{user}
A string containing the user (and, optionally, group) name of the user
as whom the server should run.  The group name can be specified in a
suffix, separated by a colon or period, i.e.@: @code{"user"},
@code{"user:group"} or @code{"user.group"}.
@item @code{program} (default: @code{"internal"})
The server program which will serve the requests, or @code{"internal"}
if @command{inetd} should use a built-in service.
@item @code{arguments} (default: @code{'()})
A list strings or file-like objects, which are the server program's
arguments, starting with the zeroth argument, i.e.@: the name of the
program itself.  For @command{inetd}'s internal services, this entry
must be @code{'()} or @code{'("internal")}.
@end table

@xref{Configuration file,,, inetutils, GNU Inetutils} for a more
detailed discussion of each configuration field.
@end deftp

@cindex Tor
@defvr {Scheme Variable} tor-service-type
This is the type for a service that runs the @uref{https://torproject.org,
Tor} anonymous networking daemon.  The service is configured using a
@code{<tor-configuration>} record.  By default, the Tor daemon runs as the
@code{tor} unprivileged user, which is a member of the @code{tor} group.

@end defvr

@deftp {Data Type} tor-configuration
@table @asis
@item @code{tor} (default: @code{tor})
The package that provides the Tor daemon.  This package is expected to provide
the daemon at @file{bin/tor} relative to its output directory.  The default
package is the @uref{https://www.torproject.org, Tor Project's}
implementation.

@item @code{config-file} (default: @code{(plain-file "empty" "")})
The configuration file to use.  It will be appended to a default configuration
file, and the final configuration file will be passed to @code{tor} via its
@code{-f} option.  This may be any ``file-like'' object (@pxref{G-Expressions,
file-like objects}).  See @code{man tor} for details on the configuration file
syntax.

@item @code{hidden-services} (default: @code{'()})
The list of @code{<hidden-service>} records to use.  For any hidden service
you include in this list, appropriate configuration to enable the hidden
service will be automatically added to the default configuration file.  You
may conveniently create @code{<hidden-service>} records using the
@code{tor-hidden-service} procedure described below.

@item @code{socks-socket-type} (default: @code{'tcp})
The default socket type that Tor should use for its SOCKS socket.  This must
be either @code{'tcp} or @code{'unix}.  If it is @code{'tcp}, then by default
Tor will listen on TCP port 9050 on the loopback interface (i.e., localhost).
If it is @code{'unix}, then Tor will listen on the UNIX domain socket
@file{/var/run/tor/socks-sock}, which will be made writable by members of the
@code{tor} group.

If you want to customize the SOCKS socket in more detail, leave
@code{socks-socket-type} at its default value of @code{'tcp} and use
@code{config-file} to override the default by providing your own
@code{SocksPort} option.
@end table
@end deftp

@cindex hidden service
@deffn {Scheme Procedure} tor-hidden-service @var{name} @var{mapping}
Define a new Tor @dfn{hidden service} called @var{name} and implementing
@var{mapping}.  @var{mapping} is a list of port/host tuples, such as:

@example
 '((22 "127.0.0.1:22")
   (80 "127.0.0.1:8080"))
@end example

In this example, port 22 of the hidden service is mapped to local port 22, and
port 80 is mapped to local port 8080.

This creates a @file{/var/lib/tor/hidden-services/@var{name}} directory, where
the @file{hostname} file contains the @code{.onion} host name for the hidden
service.

See @uref{https://www.torproject.org/docs/tor-hidden-service.html.en, the Tor
project's documentation} for more information.
@end deffn

The @code{(gnu services rsync)} module provides the following services:

You might want an rsync daemon if you have files that you want available
so anyone (or just yourself) can download existing files or upload new
files.

@deffn {Scheme Variable} rsync-service-type
This is the type for the @uref{https://rsync.samba.org, rsync} rsync daemon,
@command{rsync-configuration} record as in this example:

@example
(service rsync-service-type)
@end example

See below for details about @code{rsync-configuration}.
@end deffn

@deftp {Data Type} rsync-configuration
Data type representing the configuration for @code{rsync-service}.

@table @asis
@item @code{package} (default: @var{rsync})
@code{rsync} package to use.

@item @code{port-number} (default: @code{873})
TCP port on which @command{rsync} listens for incoming connections.  If port
is less than @code{1024} @command{rsync} needs to be started as the
@code{root} user and group.

@item @code{pid-file} (default: @code{"/var/run/rsyncd/rsyncd.pid"})
Name of the file where @command{rsync} writes its PID.

@item @code{lock-file} (default: @code{"/var/run/rsyncd/rsyncd.lock"})
Name of the file where @command{rsync} writes its lock file.

@item @code{log-file} (default: @code{"/var/log/rsyncd.log"})
Name of the file where @command{rsync} writes its log file.

@item @code{use-chroot?} (default: @var{#t})
Whether to use chroot for @command{rsync} shared directory.

@item @code{share-path} (default: @file{/srv/rsync})
Location of the @command{rsync} shared directory.

@item @code{share-comment} (default: @code{"Rsync share"})
Comment of the @command{rsync} shared directory.

@item @code{read-only?} (default: @var{#f})
Read-write permissions to shared directory.

@item @code{timeout} (default: @code{300})
I/O timeout in seconds.

@item @code{user} (default: @var{"root"})
Owner of the @code{rsync} process.

@item @code{group} (default: @var{"root"})
Group of the @code{rsync} process.

@item @code{uid} (default: @var{"rsyncd"})
User name or user ID that file transfers to and from that module should take
place as when the daemon was run as @code{root}.

@item @code{gid} (default: @var{"rsyncd"})
Group name or group ID that will be used when accessing the module.

@end table
@end deftp

Furthermore, @code{(gnu services ssh)} provides the following services.
@cindex SSH
@cindex SSH server

@deffn {Scheme Procedure} lsh-service [#:host-key "/etc/lsh/host-key"] @
       [#:daemonic? #t] [#:interfaces '()] [#:port-number 22] @
       [#:allow-empty-passwords? #f] [#:root-login? #f] @
       [#:syslog-output? #t] [#:x11-forwarding? #t] @
       [#:tcp/ip-forwarding? #t] [#:password-authentication? #t] @
       [#:public-key-authentication? #t] [#:initialize? #t]
Run the @command{lshd} program from @var{lsh} to listen on port @var{port-number}.
@var{host-key} must designate a file containing the host key, and readable
only by root.

When @var{daemonic?} is true, @command{lshd} will detach from the
controlling terminal and log its output to syslogd, unless one sets
@var{syslog-output?} to false.  Obviously, it also makes lsh-service
depend on existence of syslogd service.  When @var{pid-file?} is true,
@command{lshd} writes its PID to the file called @var{pid-file}.

When @var{initialize?} is true, automatically create the seed and host key
upon service activation if they do not exist yet.  This may take long and
require interaction.

When @var{initialize?} is false, it is up to the user to initialize the
randomness generator (@pxref{lsh-make-seed,,, lsh, LSH Manual}), and to create
a key pair with the private key stored in file @var{host-key} (@pxref{lshd
basics,,, lsh, LSH Manual}).

When @var{interfaces} is empty, lshd listens for connections on all the
network interfaces; otherwise, @var{interfaces} must be a list of host names
or addresses.

@var{allow-empty-passwords?} specifies whether to accept log-ins with empty
passwords, and @var{root-login?} specifies whether to accept log-ins as
root.

The other options should be self-descriptive.
@end deffn

@cindex SSH
@cindex SSH server
@deffn {Scheme Variable} openssh-service-type
This is the type for the @uref{http://www.openssh.org, OpenSSH} secure
shell daemon, @command{sshd}.  Its value must be an
@code{openssh-configuration} record as in this example:

@example
(service openssh-service-type
         (openssh-configuration
           (x11-forwarding? #t)
           (permit-root-login 'without-password)
           (authorized-keys
             `(("alice" ,(local-file "alice.pub"))
               ("bob" ,(local-file "bob.pub"))))))
@end example

See below for details about @code{openssh-configuration}.

This service can be extended with extra authorized keys, as in this
example:

@example
(service-extension openssh-service-type
                   (const `(("charlie"
                             ,(local-file "charlie.pub")))))
@end example
@end deffn

@deftp {Data Type} openssh-configuration
This is the configuration record for OpenSSH's @command{sshd}.

@table @asis
@item @code{pid-file} (default: @code{"/var/run/sshd.pid"})
Name of the file where @command{sshd} writes its PID.

@item @code{port-number} (default: @code{22})
TCP port on which @command{sshd} listens for incoming connections.

@item @code{permit-root-login} (default: @code{#f})
This field determines whether and when to allow logins as root.  If
@code{#f}, root logins are disallowed; if @code{#t}, they are allowed.
If it's the symbol @code{'without-password}, then root logins are
permitted but not with password-based authentication.

@item @code{allow-empty-passwords?} (default: @code{#f})
When true, users with empty passwords may log in.  When false, they may
not.

@item @code{password-authentication?} (default: @code{#t})
When true, users may log in with their password.  When false, they have
other authentication methods.

@item @code{public-key-authentication?} (default: @code{#t})
When true, users may log in using public key authentication.  When
false, users have to use other authentication method.

Authorized public keys are stored in @file{~/.ssh/authorized_keys}.
This is used only by protocol version 2.

@item @code{x11-forwarding?} (default: @code{#f})
When true, forwarding of X11 graphical client connections is
enabled---in other words, @command{ssh} options @option{-X} and
@option{-Y} will work.

@item @code{allow-agent-forwarding?} (default: @code{#t})
Whether to allow agent forwarding.

@item @code{allow-tcp-forwarding?} (default: @code{#t})
Whether to allow TCP forwarding.

@item @code{gateway-ports?} (default: @code{#f})
Whether to allow gateway ports.

@item @code{challenge-response-authentication?} (default: @code{#f})
Specifies whether challenge response authentication is allowed (e.g.@: via
PAM).

@item @code{use-pam?} (default: @code{#t})
Enables the Pluggable Authentication Module interface.  If set to
@code{#t}, this will enable PAM authentication using
@code{challenge-response-authentication?} and
@code{password-authentication?}, in addition to PAM account and session
module processing for all authentication types.

Because PAM challenge response authentication usually serves an
equivalent role to password authentication, you should disable either
@code{challenge-response-authentication?} or
@code{password-authentication?}.

@item @code{print-last-log?} (default: @code{#t})
Specifies whether @command{sshd} should print the date and time of the
last user login when a user logs in interactively.

@item @code{subsystems} (default: @code{'(("sftp" "internal-sftp"))})
Configures external subsystems (e.g.@: file transfer daemon).

This is a list of two-element lists, each of which containing the
subsystem name and a command (with optional arguments) to execute upon
subsystem request.

The command @command{internal-sftp} implements an in-process SFTP
server.  Alternately, one can specify the @command{sftp-server} command:
@example
(service openssh-service-type
         (openssh-configuration
          (subsystems
           `(("sftp" ,(file-append openssh "/libexec/sftp-server"))))))
@end example

@item @code{accepted-environment} (default: @code{'()})
List of strings describing which environment variables may be exported.

Each string gets on its own line.  See the @code{AcceptEnv} option in
@code{man sshd_config}.

This example allows ssh-clients to export the @code{COLORTERM} variable.
It is set by terminal emulators, which support colors.  You can use it in
your shell's ressource file to enable colors for the prompt and commands
if this variable is set.

@example
(service openssh-service-type
         (openssh-configuration
           (accepted-environment '("COLORTERM"))))
@end example

@item @code{authorized-keys} (default: @code{'()})
@cindex authorized keys, SSH
@cindex SSH authorized keys
This is the list of authorized keys.  Each element of the list is a user
name followed by one or more file-like objects that represent SSH public
keys.  For example:

@example
(openssh-configuration
  (authorized-keys
    `(("rekado" ,(local-file "rekado.pub"))
      ("chris" ,(local-file "chris.pub"))
      ("root" ,(local-file "rekado.pub") ,(local-file "chris.pub")))))
@end example

@noindent
registers the specified public keys for user accounts @code{rekado},
@code{chris}, and @code{root}.

Additional authorized keys can be specified @i{via}
@code{service-extension}.

Note that this does @emph{not} interfere with the use of
@file{~/.ssh/authorized_keys}.

@item @code{log-level} (default: @code{'info})
This is a symbol specifying the logging level: @code{quiet}, @code{fatal},
@code{error}, @code{info}, @code{verbose}, @code{debug}, etc.  See the man
page for @file{sshd_config} for the full list of level names.

@item @code{extra-content} (default: @code{""})
This field can be used to append arbitrary text to the configuration file.  It
is especially useful for elaborate configurations that cannot be expressed
otherwise.  This configuration, for example, would generally disable root
logins, but permit them from one specific IP address:

@example
(openssh-configuration
  (extra-content "\
Match Address 192.168.0.1
  PermitRootLogin yes"))
@end example

@end table
@end deftp

@deffn {Scheme Procedure} dropbear-service [@var{config}]
Run the @uref{https://matt.ucc.asn.au/dropbear/dropbear.html,Dropbear SSH
daemon} with the given @var{config}, a @code{<dropbear-configuration>}
object.

For example, to specify a Dropbear service listening on port 1234, add
this call to the operating system's @code{services} field:

@example
(dropbear-service (dropbear-configuration
                    (port-number 1234)))
@end example
@end deffn

@deftp {Data Type} dropbear-configuration
This data type represents the configuration of a Dropbear SSH daemon.

@table @asis
@item @code{dropbear} (default: @var{dropbear})
The Dropbear package to use.

@item @code{port-number} (default: 22)
The TCP port where the daemon waits for incoming connections.

@item @code{syslog-output?} (default: @code{#t})
Whether to enable syslog output.

@item @code{pid-file} (default: @code{"/var/run/dropbear.pid"})
File name of the daemon's PID file.

@item @code{root-login?} (default: @code{#f})
Whether to allow @code{root} logins.

@item @code{allow-empty-passwords?} (default: @code{#f})
Whether to allow empty passwords.

@item @code{password-authentication?} (default: @code{#t})
Whether to enable password-based authentication.
@end table
@end deftp

@defvr {Scheme Variable} %facebook-host-aliases
This variable contains a string for use in @file{/etc/hosts}
(@pxref{Host Names,,, libc, The GNU C Library Reference Manual}).  Each
line contains a entry that maps a known server name of the Facebook
on-line service---e.g., @code{www.facebook.com}---to the local
host---@code{127.0.0.1} or its IPv6 equivalent, @code{::1}.

This variable is typically used in the @code{hosts-file} field of an
@code{operating-system} declaration (@pxref{operating-system Reference,
@file{/etc/hosts}}):

@example
(use-modules (gnu) (guix))

(operating-system
  (host-name "mymachine")
  ;; ...
  (hosts-file
    ;; Create a /etc/hosts file with aliases for "localhost"
    ;; and "mymachine", as well as for Facebook servers.
    (plain-file "hosts"
                (string-append (local-host-aliases host-name)
                               %facebook-host-aliases))))
@end example

This mechanism can prevent programs running locally, such as Web
browsers, from accessing Facebook.
@end defvr

The @code{(gnu services avahi)} provides the following definition.

@defvr {Scheme Variable} avahi-service-type
This is the service that runs @command{avahi-daemon}, a system-wide
mDNS/DNS-SD responder that allows for service discovery and
``zero-configuration'' host name lookups (see @uref{http://avahi.org/}).
Its value must be a @code{zero-configuration} record---see below.

This service extends the name service cache daemon (nscd) so that it can
resolve @code{.local} host names using
@uref{http://0pointer.de/lennart/projects/nss-mdns/, nss-mdns}.  @xref{Name
Service Switch}, for information on host name resolution.

Additionally, add the @var{avahi} package to the system profile so that
commands such as @command{avahi-browse} are directly usable.
@end defvr

@deftp {Data Type} avahi-configuration
Data type representation the configuration for Avahi.

@table @asis

@item @code{host-name} (default: @code{#f})
If different from @code{#f}, use that as the host name to
publish for this machine; otherwise, use the machine's actual host name.

@item @code{publish?} (default: @code{#t})
When true, allow host names and services to be published (broadcast) over the
network.

@item @code{publish-workstation?} (default: @code{#t})
When true, @command{avahi-daemon} publishes the machine's host name and IP
address via mDNS on the local network.  To view the host names published on
your local network, you can run:

@example
avahi-browse _workstation._tcp
@end example

@item @code{wide-area?} (default: @code{#f})
When true, DNS-SD over unicast DNS is enabled.

@item @code{ipv4?} (default: @code{#t})
@itemx @code{ipv6?} (default: @code{#t})
These fields determine whether to use IPv4/IPv6 sockets.

@item @code{domains-to-browse} (default: @code{'()})
This is a list of domains to browse.
@end table
@end deftp

@deffn {Scheme Variable} openvswitch-service-type
This is the type of the @uref{http://www.openvswitch.org, Open vSwitch}
service, whose value should be an @code{openvswitch-configuration}
object.
@end deffn

@deftp {Data Type} openvswitch-configuration
Data type representing the configuration of Open vSwitch, a multilayer
virtual switch which is designed to enable massive network automation
through programmatic extension.

@table @asis
@item @code{package} (default: @var{openvswitch})
Package object of the Open vSwitch.

@end table
@end deftp

@node X Window
@subsection X Window

@cindex X11
@cindex X Window System
@cindex login manager
Support for the X Window graphical display system---specifically
Xorg---is provided by the @code{(gnu services xorg)} module.  Note that
there is no @code{xorg-service} procedure.  Instead, the X server is
started by the @dfn{login manager}, by default SLiM.

@cindex window manager
To use X11, you must install at least one @dfn{window manager}---for
example the @code{windowmaker} or @code{openbox} packages---preferably
by adding it to the @code{packages} field of your operating system
definition (@pxref{operating-system Reference, system-wide packages}).

@defvr {Scheme Variable} slim-service-type
This is the type for the SLiM graphical login manager for X11.

@cindex session types (X11)
@cindex X11 session types
SLiM looks for @dfn{session types} described by the @file{.desktop} files in
@file{/run/current-system/profile/share/xsessions} and allows users to
choose a session from the log-in screen using @kbd{F1}.  Packages such
as @code{xfce}, @code{sawfish}, and @code{ratpoison} provide
@file{.desktop} files; adding them to the system-wide set of packages
automatically makes them available at the log-in screen.

In addition, @file{~/.xsession} files are honored.  When available,
@file{~/.xsession} must be an executable that starts a window manager
and/or other X clients.
@end defvr

@deftp {Data Type} slim-configuration
Data type representing the configuration of @code{slim-service-type}.

@table @asis
@item @code{allow-empty-passwords?} (default: @code{#t})
Whether to allow logins with empty passwords.

@item @code{auto-login?} (default: @code{#f})
@itemx @code{default-user} (default: @code{""})
When @code{auto-login?} is false, SLiM presents a log-in screen.

When @code{auto-login?} is true, SLiM logs in directly as
@code{default-user}.

@item @code{theme} (default: @code{%default-slim-theme})
@itemx @code{theme-name} (default: @code{%default-slim-theme-name})
The graphical theme to use and its name.

@item @code{auto-login-session} (default: @code{#f})
If true, this must be the name of the executable to start as the default
session---e.g., @code{(file-append windowmaker "/bin/windowmaker")}.

If false, a session described by one of the available @file{.desktop}
files in @code{/run/current-system/profile} and @code{~/.guix-profile}
will be used.

@quotation Note
You must install at least one window manager in the system profile or in
your user profile.  Failing to do that, if @code{auto-login-session} is
false, you will be unable to log in.
@end quotation

@item @code{startx} (default: @code{(xorg-start-command)})
The command used to start the X11 graphical server.

@item @code{xauth} (default: @code{xauth})
The XAuth package to use.

@item @code{shepherd} (default: @code{shepherd})
The Shepherd package used when invoking @command{halt} and
@command{reboot}.

@item @code{sessreg} (default: @code{sessreg})
The sessreg package used in order to register the session.

@item @code{slim} (default: @code{slim})
The SLiM package to use.
@end table
@end deftp

@defvr {Scheme Variable} %default-theme
@defvrx {Scheme Variable} %default-theme-name
The default SLiM theme and its name.
@end defvr


@deftp {Data Type} sddm-configuration
This is the data type representing the sddm service configuration.

@table @asis
@item @code{display-server} (default: "x11")
Select display server to use for the greeter. Valid values are "x11"
or "wayland".

@item @code{numlock} (default: "on")
Valid values are "on", "off" or "none".

@item @code{halt-command} (default @code{#~(string-apppend #$shepherd "/sbin/halt")})
Command to run when halting.

@item @code{reboot-command} (default @code{#~(string-append #$shepherd "/sbin/reboot")})
Command to run when rebooting.

@item @code{theme} (default "maldives")
Theme to use. Default themes provided by SDDM are "elarun" or "maldives".

@item @code{themes-directory} (default "/run/current-system/profile/share/sddm/themes")
Directory to look for themes.

@item @code{faces-directory} (default "/run/current-system/profile/share/sddm/faces")
Directory to look for faces.

@item @code{default-path} (default "/run/current-system/profile/bin")
Default PATH to use.

@item @code{minimum-uid} (default 1000)
Minimum UID to display in SDDM.

@item @code{maximum-uid} (default 2000)
Maximum UID to display in SDDM

@item @code{remember-last-user?} (default #t)
Remember last user.

@item @code{remember-last-session?} (default #t)
Remember last session.

@item @code{hide-users} (default "")
Usernames to hide from SDDM greeter.

@item @code{hide-shells} (default @code{#~(string-append #$shadow "/sbin/nologin")})
Users with shells listed will be hidden from the SDDM greeter.

@item @code{session-command} (default @code{#~(string-append #$sddm "/share/sddm/scripts/wayland-session")})
Script to run before starting a wayland session.

@item @code{sessions-directory} (default "/run/current-system/profile/share/wayland-sessions")
Directory to look for desktop files starting wayland sessions.

@item @code{xorg-server-path} (default @code{xorg-start-command})
Path to xorg-server.

@item @code{xauth-path} (default @code{#~(string-append #$xauth "/bin/xauth")})
Path to xauth.

@item @code{xephyr-path} (default @code{#~(string-append #$xorg-server "/bin/Xephyr")})
Path to Xephyr.

@item @code{xdisplay-start} (default @code{#~(string-append #$sddm "/share/sddm/scripts/Xsetup")})
Script to run after starting xorg-server.

@item @code{xdisplay-stop} (default @code{#~(string-append #$sddm "/share/sddm/scripts/Xstop")})
Script to run before stopping xorg-server.

@item @code{xsession-command} (default: @code{xinitrc})
Script to run before starting a X session.

@item @code{xsessions-directory} (default: "/run/current-system/profile/share/xsessions")
Directory to look for desktop files starting X sessions.

@item @code{minimum-vt} (default: 7)
Minimum VT to use.